(CNN) -- Democratic leaders took the initiative Monday to go after one of their own, U.S. Rep. Anthony Weiner, hours after he admitted to lying about posting an explicit photo on his Twitter account and carrying on inappropriate relationships with women he'd met online.
Two Democratic sources said that Weiner, in a brief telephone conversation Monday with House Minority Leader Nancy Pelosi, made it abundantly clear that he was not going to resign. At his press conference later that day, the New York Democrat said that Pelosi was "not happy" but "also told me that she loved me and wanted us to ... pull through this."
Pelosi, D-California, who until last January was House speaker, reacted by calling for the chamber's Ethics Commission to open an investigation into the seven-term congressman "to determine whether any official resources were used or any other violation of House rules occurred."
Such a probe is rare, especially when called by a member of one's own party, the Democratic sources said.
One question that is sure to be central to such an investigation is whether Weiner used congressional resources while sending -- as he admitted -- explicit photos and messages to "about six women" over a three-year period.
The New York Democrat claimed that his BlackBerry device is not paid for by the government, and added, "I don't believe that I used any government resources" in conducting the illicit, largely electronic affairs.
In a statement, Weiner said he will "welcome and will fully cooperate with an investigation by the House Ethics Committee."
Other Democrats, many of whom initially rallied behind Weiner and his initial claim that his Twitter account had been hacked, backed Pelosi's call for an investigation.
Rep. Steve Israel, chairman of the Democratic Congressional Campaign Committee, chastised his fellow New Yorker for what he called "a deep personal failure and inappropriate behavior that embarrassed himself, his family and the House." He threw his support behind the ethics probe "to remove all remaining doubt about this situation."
Katie Grant, the spokeswoman for House Democratic Whip Steny Hoyer, told CNN that "if there have been any questions regarding ethics that have been raised in the public sphere that the Ethics Committee should look at them."
But while some Democrats are touting the ethics probe as a bold and significant step, one Republican source calls it "hollow."
The GOP source said it is noteworthy that Pelosi called for an investigation but did not demand Weiner step down -- as happened with former Rep. Chris Lee. The married Republican from western New York resigned in February, following a report that he had tried to meet a woman on Craigslist.
CNN's Kate Bolduan, Deirdre Walsh and Dana Bash contributed to this report.